Does NHibernate HQL support the UNION ALL keyword?

Question

After extensive googling, I still can't find a definitive answer to this question. Some old articles/blog posts I've seen say not at all. Some say yes if the underling database supports it. Which is it? I asked on the nhusers group with no answer so far. Any help would be appreciated.

Answer 1

HQL does not support union nor intersect. You probably can achieve it via Criteria or native SQL.

Source: https://www.hibernate.org/117.html#A21

Answer 2

I've read somewhere that it doesn't although I can't figure out why. the best way to see is to try it your self...

Answer 3

NHibernate does not support union. There is always one type in a result.

What you can do is a query to a base class or interface. NHibernate will perform a union to get all the values from all tables where the entities are mapped to.

There is also the union-subclass mapping strategy, which also implies that there is a base class or interface.